Polarizers are used for various liquid crystal displays (LCDs) for television sets, personal computers, cell-phones, etc. Usually, the polarizers are manufactured by dyeing and uniaxially-stretching polyvinyl alcohol (PVA) films. When a PVA film is uniaxially-stretched, the dichroic material adsorbed by (dyeing) the PVA molecules is oriented and thereby the PVA film becomes a polarizer.
Recently, the use of LCDs for television sets is increasing rapidly, and the size of the screens thereof also is increasing. Accordingly, there also are demands for an increase in size of polarizers that are used for television sets. The manufacture of such large-sized polarizers also results in an increase in size of, for example, the manufacturing facility. Therefore, an enormous amount of investment in facility is required.
For example, conventionally, a PVA film is immersed in baths and is stretched while being swelled, dyed, and crosslinked. Thus, a polarizer is produced. This, however, requires large baths when large-sized polarizers are to be manufactured. Furthermore, in the manufacturing method that employs baths, since the liquid concentration in each bath changes over time, cumbersome routine liquid management is necessary, and special equipment such as measuring equipment or a conditioner also is required accordingly.
Examples of the method for solving such problems include a method of spraying a liquid onto a PVA film in the gas phase. With this method, a PVA film can always be brought into contact with a fresh liquid through spraying of the liquid in the gas phase without being affected by the change of the liquid concentration over time. Moreover, since this method requires no bath, it allows the size of the manufacturing facility to be reduced.
Specifically, for example, a method of manufacturing a polarizer has been proposed in which a liquid is brought into contact with a PVA film by shower in a washing step (see Patent Document 1). Furthermore, a method of manufacturing a polarizer also has been proposed in which liquids are sprayed onto a PVA film in a dyeing step and a crosslinking step (see Patent Document 2). However, when polarizers are manufactured by these methods, there is a problem in that the polarizers curl.
[Patent Document 1] JP 2001-290027 A
[Patent Document 2] JP 2003-185834 A